the blueprint of life; from dna to protein
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The blueprint of life; from DNA to Protein. Bio 261 Medgar Evers College, CUNY Prof. Santos. DNA, the substance of inheritance Is the most celebrated molecule of our time Hereditary information Is encoded in the chemical language of DNA and reproduced in all the cells of your body - PowerPoint PPT PresentationTRANSCRIPT
The blueprint of life; from DNA to Protein
Bio 261Medgar Evers College, CUNY
Prof. Santos
• DNA, the substance of inheritance– Is the most celebrated molecule of our time
• Hereditary information– Is encoded in the chemical language of DNA
and reproduced in all the cells of your body
• It is the DNA program– That directs the development of many
different types of traits
Figure 16.7a, c
C
T
A
A
T
CG
GC
A
C G
AT
AT
A T
TA
C
TA
0.34 nm
3.4 nm
(a) Key features of DNA structure
G
1 nm
G
(c) Space-filling model
T
O
–O O
OH
O
–OO
O
H2C
O
–OO
O
H2C
O
–OO
O
OH
O
O
OT A
C
GC
A T
O
O
O
CH2
OO–
OO
CH2
CH2
CH2
5 end
Hydrogen bond3 end
3 end
G
P
P
P
P
O
OH
O–
OO
O
P
P
O–
OO
O
P
O–
OO
O
P
(b) Partial chemical structure
H2C
5 endFigure 16.7b
O
N H O CH3
N
N
O
N
N
N
N H
Sugar
Sugar
Adenine (A) Thymine (T)
N
N
N
N
Sugar
O H N
H
NH
N OH
H
N
Sugar
Guanine (G) Cytosine (C)Figure 16.8
H
DNA
The Components and Structure of DNADNA is made up of nucleotides.
A nucleotide is a monomer of nucleic acids made up of:
• Deoxyribose – 5-carbon Sugar• Phosphate Group• Nitrogenous Base
There are four kinds of bases in in DNA:adenine
guanine
cytosine
thymine
Chargaff’s rule
Chargaff's Rules
Erwin Chargaff discovered that:• The percentages of guanine [G] and cytosine [C] bases are almost
equal in any sample of DNA. – The percentages of adenine [A] and thymine [T] bases
are almost equal in any sample of DNA.
DNA Double Helix
• There are 2 hydrogen bonds between adenine and thymine and three hydrogen bonds between cytosine and guanine.
DNA to RNA to Protein connection
Protein synthesis
3 steps
1- transcription
2- RNA processing
3- translation
Transcription
• Copying the genetic code directly from DNA. • We make a single strand of messenger RNA.• We begin initiation by unwinding the double
stranded DNA and copying only one of the strands. The strand that is copied is called the sense strand. It serves as a template for the production of messenger RNA.
• Transcription begins when an enzyme called RNA polymerase binds to a special region of the DNA called promoter sequence. Unlike DNA polymerase, RNA polymerase doesn’t need a primer.
• RNA polymerase brings free floating RNA nucleotides to the sense strand.
• Guanine and cytosine pair up.
• But, there is no thymine in RNA. Another base called Uracil pairs up with adenine.
• The messenger RNA strand will continue to elongate until it reaches a termination point.
• The coding regions are called exons and the non-coding regions are called introns.
• The introns are removed by an enzyme-RNA complex known as the spliceosome.
• A tail of adenine bases is added to the 3 prime end and a modified guanine nucleotide is added to the 5 prime end.
• Once the messenger RNA has been processed, it is ready to leave the nucleus and bind to a ribosome.
• The mature messenger RNA carries the message from DNA in the forms of codons.
• A codon is a group of 3 bases that correspond to one of the 20 amino acids.
• There are 64 possible codons and only 20 amino acids. There is redundancy with some of the amino acids!
• The initial codon is AUG or methionine and there are three stop codons, UAA, UGA and UAG.
Figure 17.5
Second mRNA baseU C A G
U
C
A
G
UUUUUCUUAUUG
CUUCUCCUACUG
AUUAUCAUAAUG
GUUGUCGUAGUG
Met orstart
Phe
Leu
Leu
lle
Val
UCUUCCUCAUCG
CCUCCCCCACCG
ACUACCACAACG
GCUGCCGCAGCG
Ser
Pro
Thr
Ala
UAUUAC
UGUUGC
Tyr Cys
CAUCACCAACAG
CGUCGCCGACGG
AAUAACAAAAAG
AGUAGCAGAAGG
GAUGACGAAGAG
GGUGGCGGAGGG
UGGUAAUAG Stop
Stop UGA StopTrp
His
Gln
Asn
Lys
Asp
Arg
Ser
Arg
Gly
U
CA
GUCAG
UCAG
UCAG
Fir
st m
RN
A b
ase
(5
end
)
Th
ird
mR
NA
bas
e (3
en
d)
Glu
Translation
• The messenger RNA attaches to the ribosome and the message in the form of codons is “translated” and the appropriate amino acid is put in place.
• A molecule of RNA called transfer RNA brings along the amino acid. It resembles a four leaf clover.
• On the top is the amino acid and on the bottom is a sequence known as the anti codon.
3
CCACGCUUAA
GACACCU*
GC
* *G U G U *CU
* G AGGU**A
*A
A GUC
AGACC*
C G A GA G G
G*
*GA
CUC*AUUUAGGCG5
Amino acidattachment site
Hydrogenbonds
Anticodon
A
• The anticodon pairs up with the codon. This allows the amino acids to put placed in the correct sequence or order.